Particles, Strings and Cosmology (PASCOS 99)

The following sections are included:

• PREFACE

• LOCAL ORGANIZING COMMITTEE

• SUBTOPIC CONVENORS AND CONSULTANTS

• TABLE OF CONTENTS

We review recent progress in constructing realistic brane models from type I string vacua. Explicit models with three families of the standard model gauge group and its left-right generalizations are presented with supersymmetry broken at the string scale of order M_s ~ 10^10-12 GeV, realizing gravity mediated supersymmetry breaking at low energies. Unification of couplings occurs at the string scale due to the particular U(1) normalizations of D-branes, as well as to the existence of a Higgs field per family of quarks and leptons. The proton is naturally stable due to intrinsic discrete symmetries of the corresponding string theory. In particular R-parity appears as a natural stringy symmetry. There are axionic fields with the right couplings as to solve the strong CP problem. Similar realizations are also presented for a string scale of 1 TeV, although without solving the gauge unification problem. Open questions are briefly discussed.

It is argued that stochastic quantization underlies the relation between string theory and gauge theories, with Maldacena's AdS/CFT conjecture as a particular case. The gauge invariant Schwinger-Dyson operator is identified with the Wheeler-DeWitt operator of quantum gravity, enabling a construction of gauge theory operators as bulk operators. The string field theory Hamiltonian identified in this manner is used to exhibit a nonperturbative background-independent dynamical truncation of the string spectrum. The work described in this talk was mostly carried out in collaboration with Gilad Lifschytz.

We give a brief summary of present bounds on the size of possible extra-dimensions as well as the string scale from collider experiments.

We review some aspects of moduli in string theory. We argue that one should focus on approximate moduli spaces, and that there is evidence that such spaces exist non-perturbatively. We ask what it would mean for string theory to predict low energy supersymmetry. Aspects of two proposed mechanisms for fixing the moduli are discussed, and solutions to certain cosmological problems associated with moduli are proposed.

In this talk, we discuss recent developments concerning the possibility of large extra spacetime dimensions. After briefly outlining how such dimensions can lower the fundamental GUT, Planck, and string scales, we then review how these scenarios lead to a new higher-dimensional seesaw mechanism for generating neutrino oscillations — perhaps even without neutrino masses. We also discuss how extra dimensions lead to new mechanisms contributing to the "invisibility" of the QCD axion.

Non-supersymmetric black holes carrying both electric and magnetic charge with respect to a single Kaluza-Klein gauge field have much in common with supersymmetric black holes. Angular momentum conservation and other general physics principles underlies some of their basic features. Kaluza-Klein black holes are interpreted in string theory as bound states of D6-branes and D0-branes. The microscopic theory reproduces the full nonlinear mass formula of the extremal black holes.

We examine the cosmology of compact brane models. In the absence of a stabilization mechanism for the radius of the extra dimension the cosmology will generically differ from the ordinary FRW Universe due to the presence of the extra massless field in the low-energy theory. Once the radius is stabilized, the ordinary 4D cosmology is recovered. For the case of the Randall-Sundrum model we examine the kinematics of the radion field, and find that corrections to the standard FRW equations are small for temperatures below the weak scale. We find that the radion field has renormalizable and unsuppressed couplings to Standard Model particles after electroweak symmetry breaking. These couplings may have important implications for collider searches.

A new covariant "causal entropy bound" on entropy within a generic space-like region of volume V, and energy E scales as , the geometric mean of Bekenstein's S/ER and holographic S/A bounds, R being the linear size and A the boundary area of the region. In the case of limited gravity, Bekenstein's bound is the strongest while naive holography is the weakest. In the case of strong gravity, causal entropy bound and Bousso's holographic bound are stronger than Bekenstein's, while naive holography is too tight, and hence typically wrong. A new generalized second law of thermodynamics in cosmology, based on the conjecture that causal boundaries and not only event horizons have geometric entropies proportional to their area, forbids certain cosmological singularities, and is compatible with entropy bounds. In string cosmology the second law provides new information about non-singular solutions.

We discuss spacetime singularity resolution in the context of the gravity / gauge correspondence, for brane systems giving rise to gauge theories with eight supercharges and no hypermultiplets. For N ≫ 1 D-branes wrapped on K3 there is a naked 'repulson' singularity in the classical spacetime, if the branes are assumed to be coincident. In fact, stringy effects give rise to a kind of exclusion principle so the branes live on a spherical locus of enhanced SU(2) gauge symmetry. The exclusion phenomenon excises the repulson singularity in spacetime, and in the nonperturbative gauge theory it can be seen via the Seiberg-Witten curve.

The MSSM predicts the existence of a relatively light Higgs boson ɸW with Standard Model–like couplings to W and Z bosons. Observation or exclusion of ɸW would be a test of whether Supersymmetry is the source of Electroweak Symmetry Breaking. Discovery of the charged or CP–odd Higgs boson will not help in this respect. I demonstrate how various choices of the MSSM parameters can compromise the standard Higgs boson searches for a Standard Model–like Higgs boson at the Tevatron or at the LHC, but not at both simultaneously. The channel at the Tevatron is complementary to at the LHC.

This talk focuses on the phases of the soft-breaking Lagrangian, and their possible connections to CP violation. I explain why the phases may be large, discuss how they are measurable and a variety of effects they may have.

We discuss a heterotic–string solution in which the observable sector effective field theory just below the string scale reduces to that of the MSSM, with the standard observable gauge group being just SU(3)_C × SU(2)_L × U(1)_Y and the SU(3)_C × SU(2)_L × U(1)_Y–charged spectrum of the observable sector consisting solely of the MSSM spectrum. Associated with this model is a set of distinct flat directions of vacuum expectation values (VEVs) of fields that all produce solely the MSSM spectrum. Some of these directions only involve VEVs of non–Abelian singlet fields while others also contain VEVs of non-Abelian charged fields.

I contemplate the possibility that the mismatch between the maximally symmetric point (the free fermionic point) and the strictly self–dual point in the Narain moduli space plays a role in string vacuum selection. The role of self–duality in the recent formulation of quantum mechanics from an equivalence postulate, and the new perspective that it offers on the foundations of quantum gravity and the origin of mass, are discussed.

A new framework is proposed for mediating supersymmetry breaking through an extra dimension. It predicts positive scalar masses and solves the supersymmetric flavor problem. Supersymmetry breaks on a "source" brane that is spatially separated from a parallel brane on which the standard model matter fields and their superpartners live. The gauge and gaugino fields propagate in the bulk, the latter receiving a supersymmetry breaking mass from direct couplings to the source brane. Scalar masses are suppressed at the high scale but are generated via the renormalization group. The spectrum as a function of the compactification scale is also briefly discussed.

It is shown that in the Standard Model, the property of charge quantization holds for a Higgs with arbitrary isospin and hypercharge. These defining quantum numbers of the Higgs remain unconstrained while the whole basic and fundamental structure of the Standard Model remains intact. Hence it is shown that the Higgs cannot be a physical particle. Higgs is the underlying 'vacuum' over which the whole edifice of the Standard Model stands. Also on most general grounds it is established here that as per the Standard Model there is no electric charge above the electro-weak phase transition temperature. Hence there was no electric charge present in the Early Universe. The Superstring Theories are flawed in as much as they are incompatible with this requirement.

A derivation of the Randall–Sundrum's model as an effective description of the dynamics of the low-energy spectrum of string theories is given. The geometry can be described in terms of effective cosmological constants in the bulk and on the brane when the dilaton coupling vanishes and these cosmological constants are quantized.

I review some recent work, carried out by myself and various collaborators, on the non-linear gravitational aspects of the Randall-Sundrum scenario.

We review the possibilities that the Kaluza-Klein excitations of graviton states induce electroweak symmetry breaking and that electroweak symmetry breaking could have a large impact on KK phenomenology.

We present single-brane cosmological solutions that arise in the framework of the brane-world scenario in the cases of zero or non-zero cosmological constants. We address the problems of the recovery of the 4D Friedmann equation and of the compactification, as well as stabilization, of the extra dimension and we demonstrate that all of them can find a natural solution in the framework of our analysis.

In this talk, I briefly review collider signatures for two models of extra dimensions. The first one was proposed by Arkani-Hamed et al. that gravity is free to propagate in extra dimensions of very large size (≲ 1 mm). Collider signatures for this model can be divided into two types: (i) emission of real gravitons into extra dimensions, and (ii) exchanges of virtual gravitons. The second model was proposed by Pomarol et al. and Dienes et al. that the SM gauge bosons are allowed to propagate in extra dimensions. Collider signatures for the second model are due to the existence of the Kaluza-Klein (KK) states of γ, W, Z, and g bosons.

Electroweak symmetry breaking may be naturally induced by the observed quark and gauge fields in extra dimensions without a fundamental Higgs field. We show that a composite Higgs doublet can arise as a bound state of (t, b)_L and a linear combination of the Kaluza-Klein states of t_R, due to QCD in extra dimensions. The top quark mass depends on the number of active t_R Kaluza-Klein modes, and is consistent with the experimental value.

We show that the Dirac equation can be rewritten as a relation describing the fundamental symmetry group of special topological manifold corresponding to the Dirac wave field. It leads to unification of the time-space and internal symmetries wihin one symmetry group. We suppose that nonelectromagnetic interactions appear within such approach as the deviations of the metrics from the euclidean form. The expression for the long-range part of "effective" nucleon-nucleon potential is derived using this assumption.

We briefly review the phenomenological implications of the minimal supersymmetric standard model (MSSM) with explicit radiative breaking of CP invariance in the Higgs sector for the LEP2 and Tevatron colliders.

CP violation by soft supersymmetry-breaking terms in orbifold compactifications is investigated. We include the universal part of the moduli dependent threshold corrections in the construction of the non-perturbative effective potential due to gaugino-condensation. This allows interpolation of the magnitude of CP violating phases between the weakly and strongly coupled regimes.

Three different methods, using B_d → J/ψK_S, J/ψK_Sπ⁰, B_d → K^-π⁺, π⁺π^- and B_u → K^-π⁰, , π^-π⁰, to extract hadronic model independent information about new physics are discussed in this talk.

The Minimal Supersymmetric Standard Model can possess several CP-violating phases beyond the conventional Cabibo-Kobayashi-Maskawa phase. We calculate the contribution of these phases to T-violating nuclear forces. These forces induce a Schiff moment in the ¹⁹⁹Hg nucleus, which is strongly limited by experiments aimed at the detection of the electric dipole moment of the mercury atom. The result for d_Hg is found to be very sensitive to the CP-violating phases of the MSSM and the calculation carries far fewer QCD uncertainties than the corresponding calculation of the neutron EDM. We present combined constraints from the mercury and electron EDMs to limit both CP-violating phases of the MSSM.

The reconstruction of the chargino sector by measuring the cross sections with polarized beams at e⁺e^- collider experiments: , is summarised. The closure of the two–chargino system can be investigated by analysing sum rules for the production cross sections.

Angular and energy distributions for leptons and bottom quarks in the process have been calculated assuming the most general top-quark couplings. The double distributions depend both on modification of the production and decay vertices. However, the leptonic angular distribution turned out to be insensitive to non-standard parts of Wtb vertex. The method of optimal observables have been used to estimate sensitivity of future measurements at linear e⁺e^- colliders to top-quark couplings.

We study a possibility of a measurement of muon Yukawa couplings in s-channel Higgs boson production at a muon collider with transversely polarized beams. We investigate sensitivity to the relative size of the CP-odd and CP-even muon Yukawa couplings. Provided the event rate observed justify the operation of the μ⁺μ^- Higgs boson factory, we have found that polarization degree 40% is sufficient to resolve the CP nature of a single resonance as well as disentangle it from two overlapping CP conserving resonances.

The first measurements of CP violation in the B system will probably extract sin 2α, sin 2β and cos 2γ. Assuming that the CP angles α, β and γ are the interior angles of the unitarity triangle, this determines the angle set (α, β, γ) up to a twofold discrete ambiguity. The presence of this discrete ambiguity can make the discovery of new physics difficult: if only one of the two solutions is consistent with constraints from other measurements in the B and K systems, one is not sure whether new physics is present or not. I present examples of this situation, and discuss ways to resolve the discrete ambiguity.

We combine direct flavor violation smoothly with neutrino oscillations in a unified parmetrization of neutrino appearance and disappearance. We show how high purity muon and electron neutrino and antineutrino beams considered in proposals for muon colliders could provide order of magnitude improvements in probing direct lepton flavor violation, including CP violation.

The triangular basis is proposed as an efficient way of analyzing general quark mass matrices. Applying the method to hermitian hierarchical matrices with five texture zeros, analytic predictions for quark mixing can be readily obtained. One unique texture pair is found most favorable with present data. Some remarks are also made concerning parallel textures between the up and down quark mass matrices with four zeros.

We discuss the origin of "focus points" in the scalar mass RGEs of the MSSM and their implications for collider searches. We present a new exact analytic solution to the homogeneous system of scalar mass RGEs in the MSSM for general tan β. This is then used to prove that the focus point for depends only on the value of the top Yukawa coupling at the weak scale (not its value at the GUT scale) and is independent of the bottom Yukawa coupling.

At moderate to large tan β, it is no longer possible to simultaneously diagonalize the masses of quarks and their couplings the neutral Higgs bosons. The resulting flavor violations of the form and do not generate large meson–antimeson mixing amplitudes but do generate large contributes to rare decays such as B_s → μμ. Run II of the Tevatron willl probe a large region of interesting MSSM parameter space through this decay channel. This talk is based on results obtained with K.S. Babu and presented in [1].

We study the phenomenology of a class of models describing modular invariant gaugino condensation in the hidden sector of a low-energy effective theory derived from the heterotic string. Placing simple demands on the resulting observable sector, such as a supersymmetry-breaking scale of approximately 1 TeV, results in significant restrictions on the possible configurations of the hidden sector.

I summerize results of two-loop effective potential calculations of the lightest CP-even Higgs boson mass in the minimal supersymmetric standard model.

Though LEP II direct searches still cannot exclude a chargino nearly degenerate with the lightest neutralino if its mass is only slightly above half of the Z boson mass and the sneutrino is light, it can be excluded indirectly analyzing precision data. In this particular limit simple analytical formulas for oblique electroweak radiative corrections are presented.

The existence of extra chiral generations is strongly disfavored by the precision electroweak data if all the extra fermions are heavier than m_z. However fits as good as the SM can be obtained if one allows the new neutral leptons to have masses close to 50 GeV. In the framework of SUSY models precision measurements cannot exclude one additional generation of heavy fermions if chargino and neutralino have masses around 60 GeV with .

We study the feasibility of incorporating the popular Zee model for neutrino mass in the framework of the supersymmetric standard model. While a singlet slepton has the right quantum number to play the role of the Zee charged scalar boson, the SUSY framework introduces extra contributions. We derive conditions for the Zee contributions to dominate, hence retaining the flavor of the Zee model.

A new theory yields unconventional results for the angular distribution of products like jets in Higgs decays.

There is overwhelming evidence that most of the dark matter is non-baryonic, from a combination of primordial nucleosynthesis and Lyman alpha forest modelling, which yield a baryon density Ω_b ≈ 0.03, and local dynamical measurements, which yield a total matter density Ω_m ≈ 0.3. Gravitational microlensing suggests that at least 80% of the mass in galaxy halos is non-baryonic. Weakly interacting massive particles (WIMPS) are commonly considered to be the best motivated candidate for non-baryonic dark matter. We may therefore consider indirect detection of halo non-baryonic dark matter in the form of WIMPS to provide a means of studying the spatial distribution of cold dark matter. High resolutions simulations of cold dark matter have demonstrated that the dark matter is clumpy, and has a central density cusp. I will review how dark matter annihilations may yield a unique probe of the nature of cold dark matter.

The properties of nearby galaxy cluster limit the range of cosmological paramaters consistent with our universe. We describe the limits which arise from studies of the intracluster medium (ICM) mass fraction f_ICM and consideration of the possible sources of systematic error: at 95% confidence. We emphasize that independent of Type Ia supernovae (SNe Ia) observation, this cluster study, taken together with published cosmic microwave background (CMB) anisotropy studies, indicates a non-zero quintessence or dark energy component Ω_Q > 0.

We then discuss future galaxy cluster surveys which will probe the abundance of galaxy clusters intermediate and high redshift. We investigate the sensitivity of these surveys to the cosmological density parameter Ω_M and the equation of state parameter w of any quintessence component. In particular, we show that cluster survey constraints from a proposed large solid angle X-ray survey are compatable in precision and complementary in nature to constraints expected from future CMB anisotropy and SNe Ia studies.

I review recent constraints on the cosmological neutrino density Ω_ν, the cosmological constant Ω_Λ, the average matter density Ω_m, and the baryonic matter density Ω_b. The evidence currently favors the age of the universe t₀ ≈ 13 Gyr, the Hubble parameter h ≈ 0.65, 0.001 < Ω_ν < 0.1, Ω_Λ ≈ 0.7, Ω_b = 0.02h^-2, and Ω_m ≈ 0.4 ± 0.1.

The following sections are included:

• Introduction

• The Galaxy Power Spectrum

• Early Results from the SDSS

• Acknowledgement

• References

We review the current state of observations of the angular power spectrum of anisotropies in the cosmic microwave background. We describe the Boomerang program, including observations, recent results, and potential power to characterize the angular power spectrum as an example of the new generation of efforts now nearing fruition.

We investigate a leptogenesis via decays of heavy Majorana neutrinos in the framework of supersymmetry. We consider that these heavy Majorana neutrinos are produced non-thermally in inflaton decays after the inflation ends. It is shown that we can obtain sufficient lepton asymmetry to account for the baryon asymmetry of the present universe. The reheating temperature of inflation may be taken as T_R ≃ 10⁶ GeV, which is low enough to avoid the cosmological gravitino problem in the gravitino mass region m_3/2 ≃ 100GeV-1 TeV.

We investigate the evolution of the global(axionic) string network in the radiation dominated universe by use of numerical simulations in 3+1 dimensions. We find that the global string network settles down to the scaling regime where the energy density of global strings, ρ_s, is given by ρ_s = ξμ/t² with μ the string tension per unit length and the scaling parameter, ξ ~ (0.9 – 1.3), irrespective of the cosmic time. We also find that the loop distribution function can be fitted with that predicted by the so-called one scale model. Concretely, the number density, n_l(t), of the loop with the length, l, is given by n_l(t) = ν/[t^3/2(l + κt)^5/2] where ν ~ 0.0865 and κ is related with the Nambu-Goldstone(NG) boson(axion) radiation power from global(axionic) strings, P, as P = κμ with κ ~ 0.535. Therefore, the loop production function also scales and the typical scale of produced loops is nearly the horizon distance. Thus, the evolution of the global(axionic) string network in the radiation dominated universe can be well described by the one scale model in contrast with that of the local string network. Furthermore, the power spectrum of axions radiated from axionic strings is calculated from the simulation data, which is found to be highly peaked around the Hubble scale, and a more accurate constraint on the Peccei-Quinn breaking scale is obtained.

A novel solution to the cosmological horizon problem in the context of standard model particles confined to a 3-brane is presented. Furthermore, general kinematic constraints to cosmologically viable metrics of such extra dimensional brane cosmology are discussed.

We study the formation of Q-balls which are made of those flat directions that appear in the supersymmetric extension of the standard model in the context of both the gauge- and the gravity-mediated supersymmetry breaking. The full non-linear calculations for the dynamics of the complex scalar field are made. Since the scalar potential in this model is flatter than ɸ², we have found that fluctuations develop and go non-linear to form non-topological solitons, Q-balls.

I review the mechanism of electroweak baryogenesis within the framework of a string motivated supersymmetric extension of the Standard Model with large flavor-independent CP-violating phases. Possible implications for the Higgs sector are considered in correlation with the properties of the right-handed stop. I also comment on the compatibility of supersymmetric electroweak baryogenesis with various CP-violating observables.

In a model recently proposed by Albrecht and Skordis¹ it was suggested that the observed accelerated expansion of the universe could be caused by a scalar field which is trapped in a local minimum of an exponential potential modified by a polynomial prefactor. We show that scalar field cosmologies with this kind of local minimum in the potential are stable and do not decay to the true vacuum if they fulfill the observational constraints from the Type Ia Supernovae experiments. Further we briefly sketch how this potential could be related to a potential of interacting D-branes.

I review a number of particle-physics models that lead to the creation of magnetic fields in the early universe and address the complex problem of evolving such primordial magnetic fields into the fields observed today. Implications for future observations of the Cosmic Microwave Background (CMB) are briefly discussed.

We show how observations of the evolution of the galaxy cluster number abundance can be used to constrain primordial non-gaussianity in the universe. We carry out a maximum likelihood analysis incorporating a number of current datasets and accounting for a wide range of sources of systematic error. Under the assumption of gaussianity, the current data prefer a universe with matter density Ω_m ≃ 0.3 and are inconsistent with Ω_m = 1 at the 2σ level. If we assume Ω_m = 1, the predicted degree of cluster evolution is consistent with the data for non-gaussian models where the primordial fluctuations have at least two times as many peaks of height 3σ or more as a gaussian distribution does. Given an independent measurement of Ω_m, the techniques described here represent a powerful tool with which to constrain non-gaussianity in the primordial universe, independent of specific details of the non-gaussian physics.

The inflation-inspired flat, cold dark matter-dominated models of structure formation with adiabatic, nearly scale-invariant initial conditions agree very well with current CMB anisotropy data. The success of these models is highlighted by the failure of alternatives. CMB data will soon be of sufficient quality that, if one assumes inflation, one can detect a non-zero cosmological constant by combining a determination of the peak location with Hubble constant measurements.

Clumped dark matter arises naturally within the framwork of generic cosmological dark matter models. Invoking the existence of dark matter clumps can also solve many unexplained mysteries in astrophysics and geology or geophysics, eg. the galactic gamma-ray halo and the periodic terrestrial flood basalt volcanic episodes which in turn explain the mass extinctions. Clumped dark matter is dynamically stable to friction and will not heat the disk. Such clumps may have already been discovered in the form of dwarf spheroids.

A neutrino mass-mixing scheme which successfully avoids the "alpha effect," allowing r-process nucleosynthesis in the neutrino-heated ejecta of supernovae, quite independently requires the same parameters as the scheme which best fits all current indications for neutrino mass. The significance for particle physics is this independent evidence for (1) at least one light sterile neutrino, ν_s; (2) a near maximally-mixed ν_μ-ν_τ, doublet split from a lower mass ν_μ-ν_s, doublet; (3) ν_μ-ν_e, mixing ≳ 10^-4 and (4) a splitting between the doublets (measured by the ν_μ-ν_e, mass difference) ≳ 1 eV², favoring the upper part of the LSND range. If correct, it is tantalizing that neutrinos with tiny masses which mix with sterile species have profound effects on massive objects and the creation of the heaviest elements.

Microlensing of unresolved stars, often referred to as pixel microlensing, offers a unique method for detecting dark objects at least as far away as the Virgo cluster. Primordial black holes, white dwarfs, neutron stars and brown dwarf stars are all interesting possibilities in this context. We show that the Einstein time, used in classical microlensing surveys but unmeasurable in pixel microlensing, is not necessary: an easily measured timescale that is effectively the Einstein time multiplied by the flux of the source star is sufficient to extract the physical parameters.

Upcoming redshift surveys will open a remarkable new window on cosmology and the evolution of structure. We describe our procedure for estimating the velocity dispersion of the galaxy distribution on small scales. Unlike the traditional pair velocity dispersion σ₁₂, our statistic σ₁ is object weighted. This reduces the influence of rare, rich clusters of galaxies, yielding a more robust and reliable statistic. The application of σ₁ and the cosmic energy equation to the Las Campanas survey strongly prefers models with low matter density, Ω_m ~ 0.2–0.3. Statistics such as σ₁ should prove useful in upcoming redshift surveys such as the Deep Extragalactic Evolutionary Probe (DEEP), which will probe the evolution of cosmic structure to z ~ 1. In addition, DEEP may be able to achieve a measurement of the Alcock-Paczynski effect as well as obtaining significant constraints on cosmological parameters through the classic volume-redshift test.

Although high energy neutrino astronomy is a multidisciplinary science, gamma ray bursts have become the theoretical focus since recent astronomical observations revealed their potential as cosmic particle accelerators. This spotlight is shared with investigations of the potential of high energy telescopes to observe oscillating atmospheric neutrinos. The Superkamiokande results have boosted atmospheric neutrinos from a calibration tool and a background for doing astronomy, to an opportunity to confirm the evidence for neutrino mass. Nevertheless, the highlights are mostly on the experimental front with the completion of the first-generation Baikal and AMANDA detectors. Neutrino signals from the Lake Baikal detector bode well for the flurry of activities in the Mediterranean.

The status and prospects of current and near-future accelerator neutrino oscillation experiments are reviewed. The experiments discussed are: the short-baseline experiments LSND, KARMEN, and MiniBooNE, and the long-baseline experiments K2K and MINOS.

Ultra-high-energy, > 10¹⁹ eV, cosmic-ray and high energy, ~ 10¹⁴ eV, neutrino production in GRBs is discussed in the light of recent GRB and cosmic-ray observations. Emphasis is put on model predictions that can be tested with operating and planned cosmic-ray and neutrino detectors, and on the prospects of testing for neutrino properties.

Recent evidence for neutrino oscillations has revolutionized the study of neutrino masses and mixing. This report gives an overview of what we are learning from the neutrino oscillation experiments, the prospects for the near term, and the bright future of neutrino mass studies.

Recent data on solar and atmospheric neutrinos and their constraints on the neutrino mass and mixing are presented. Especially, the results from a 50 kton water Cherenkov detector, Super-Kamiokande, are discussed in detail.

We review the status of dark matter in the Minimal Supersymmetric Standard Model (MSSM). We show that Higgsinos have been excluded as dark matter candidates by the most recent LEP limits. We examine the cosmological constraints on a gaugino-type neutralino and demonstrate the important effects of neutralinoslepton coannihilation.

Dark matter is one of the central issues at the interface between astrophysics and particle physics. Here I review the current status of experimental searches for both baryonic and particle dark matter, with a focus on the direct detection of weakly interacting massive particles.

There appear to be three challenges that any theory of dark matter must face: (i) why is Ω_DM of the same order as Ω_Baryons ? (ii) what are the near solar mass objects (~ 0.5M_⊙) observed by the MACHO microlensing project ? and (iii) understanding the shallow core density profile of the halos of dwarf as well as low surface brightness galaxies. The popular cold dark matter candidates, the SUSY LSP and the axion fail to meet these challenges. We argue that in the mirror model suggested recently to explain the neutrino anomalies, the mirror baryons being 15-20 times heavier than familiar baryons, can play the role of the cold dark matter and provide reasonable explanation of all three above properties without extra assumptions.

We explore the implications of imposing the constraint that two neutrino flavors (which for definiteness we take to be ν_μ and ν_τ) are similarly coupled to the mass basis in addition to the unitarity constraints. Implications of this scheme for specific experimental situations are discussed.

It appears now more than ever before that neutrinos oscillate. For the three neutrino species, all oscillation data can be accounted for by a mass matrix that is symmetric and has vanishing diagonal elements. In direct analogy with the oscillations observed in the K⁰ — K⁰ system, it is argued that neutrino oscillations suggest that neutrinos (and their charged partners) may be composite particles.

If the mixing angles in each of the seesaw sectors are all small, and the neutrino masses are hierarchical, we study the conditions for large neutrino mixing using triangular matrices. In particular, the implication of the neutrino oscillation data for the mass hierarchy in the heavy Majorana sector is examined, and the heavy Majorana scales are shown to depend sensitively on the solar mixing angle.

Cosmic ray antiprotons have been detected for over 20 years and are now measured reliably. Standard physics predicts a spectrum and abundance of secondary antiprotons consistent with all current measurements, placing limits on non-standard antiproton properties and soon on exotic Galactic antiproton sources. Future experiments and theoretical developments are discussed.

The lepton asymmetry created in the out-of-equilibrium decay of a heavy Majorana neutrino can generate the cosmological baryon asymmetry Y_B when processed through fast anomalous electroweak reactions. In this work I examine this process under the following assumptions: (1) maximal ν_μ-ν_τ mixing (2) hierarchical mass spectrum m₃ ≃ 5 × 10^-2 eV ≫ m₂ ≫ m₁ (3) small-angle MSW solution to the solar neutrino deficit. For a variety of textures for the Dirac neutrino yukawa matrix, these constraints imply a lower bound of 10^l0 – 10¹² GeV for the lightest right-handed neutrino. The results are insensitive to the masses of the heavier right-handed neutrinos.

Highlights are presented of the latest measurements from the H1 and ZEUS experiments at HERA.

The latest results based on an analysis of the data collected by the four LEP experiments are presented. Emphasis is given to the results of searches for new physics coming from a preliminary analysis of the 235pb^-1 of data recorded in 1999, by each experiment, at centre-of-mass energies between 188.6 and 201.6 GeV.

Results for Searches for new phenomena wit the DØ detector are presented. The DØ detector upgrade and its physics potential for particle searches are described

We present here recent CDF searches for new phenomena in Run I data. The scalar top and scalar bottom quarks searches are described in the framework of supersymmetric models. We also discuss CDF limits on the Higgs boson and continuum and resonantly produced leptoquarks. Run II starting in March 2001 will allow us to considerably improve the Tevatron reach in all these channels.

Progress in the development of an experimental program for a future TeV-scale e⁺ e^- linear collider is discussed. We focus here on the research in Japan and North America, where the program is based on linear colliders in which the leading technology for acceleration uses non-superconducting X-band RF cavities. Three distinct but intimately related research areas are discussed: the accelerator, the physics prospects, and the detector issues.

The prospect of a muon accelerator facility leading eventually to a multi-TeV muon collider has in recent years attracted a strong physics interest, which has motivated a research and development effort towards the design of such an accelerator. In this note, the status of the design study is presented, and the physics potential of the machine is discussed. The main focus of the discussion is on the first stage of the facility, which is envisioned to be a storage ring with the purpose of providing intense neutrino beams. In addition, future plans for the design and physics studies are outlined.

A precise measurement of the strange quark forward-backward asymmetry around Z⁰ peak is presented. It is based on 3.2M multihadronic events collected by the DELPHI experiment from 1992 to 1995. The ring imaging Cherenkov detectors in the barrel and end-cap regions identify high energy charged kaons which tag the s quark. The s quark asymmetry is measured at different centre-of-mass energies. From the s quark pole asymmetry the electroweak mixing angle and the parity violating coupling of the s quark to the Z⁰ are determined.

Topological, exclusive and semi-exclusive hadronic τ branching fractions were measured by the DELPHI experiment at LEP. τ polarisation and asymmetries were also determined.

Some of the last experimental results on B-hadron properties obtained by the LEP,SLD and CDF experiments are presented. Several results are preliminary.

A search for charginos with masses close to the mass of the lightest neutralino is reported, based on the data collected with the DELPHI detector at LEP from 1995 to 1998 at centre-of-mass energies between 130 and 189 GeV. No excess of events with respect to the Standard Model expectations was observed, and limits in the plane of chargino-neutralino mass difference versus chargino mass are given.

DELPHI measurements of leptonic branching ratios, lifetime and the Lorentz structure in τ decays are presented. Comparisons to Standard Model predictions are performed. It is also shown how the results constrain certain extensions to the Standard Model.

LEP2 collider proves to be an excellent scientific environment for W^± physics measurements. Analyses and recent results on production cross-section, branching ratios, mass reconstruction and triple gauge boson couplings obtained on data recorded by the DELPHI experiment are presented.

Searches for physics beyond the Standard Model (SM) with the DELPHI detector at LEP 2 are discussed. Covered topics include indirect searches, single photon final states, compositeness, heavy stable particles and exotic Higgs bosons.

The latest preliminary combined results of the Higgs boson searches from the LEP experiments ALEPH, DELPHI, L3 and OPAL are presented. A general scan of the MSSM parameters is performed and leads to stringent lower mass limits and for the first time excludes low tan β values.

Recent results on searches for new particles at the electron-proton collider HERA are reported using 47 pb^-l of e⁺p collisions and 16 pb^-1 of e^-p collisions at the centre of mass energy . No evidence of new physics beyond the Standard Model was observed. Exclusion limits on resonant production of leptoquark, squark in R-parity violating supersymmetry and excited fermion are presented.

The Compact Muon Solenoid (CMS) experiment at the future CERN Large Hadron Collider, studying proton collisions at , will have a rich potential for new physics within and beyond the Standard Model. We present here an overview of proposed Minimal Super-symmetric Standard Model Higgs boson searches using the ττ decay channel. The expected reach in the MSSM parameter space is discussed in the context of extensive studies of CMS SUSY discovery potential.

A precision experiment to directly measure the recoil energy spectrum after nuclear beta decay is being set up. This will be the first time that these recoiling nuclei can be measured directly for a wide variety of nuclides. The central idea is to have the beta decay happen in an ion trap and to measure the recoiling daughter nuclei with a retardation spectrometer. First, the focus will be on measuring the recoil energy spectrum in pure Fermi beta decays and in the beta decay of mirror nuclei. From these the beta-neutrino angular correlation can be determined. Deviations from the expected spectral shape will point to physics beyond the standard electroweak model. For Fermi beta decays the experiment will be sensitive to a possible scalar weak interaction. Details of the apparatus and the current status of the project will be presented.

A subset of electroweak physics results from SLD is presented. Particular emphasis is given to the final result for A_LR, including experimental crosschecks performed in the final 1998 run. A cumulative A_LR result for all data is given. Also presented are the polarized forward-backward asymmetries for charm and bottom. Comparisons to LEP measurements and the Standard Model are given.

The following sections are included:

• Conference Schedule

• LIST OF PARTICIPANTS